Multilayer thick-film hybrid circuits method and process for constructing same

Abstract

A method and process of screening multilayer thick-film structures to produce complex hybrid electronic circuits. After deposition, drying and firing of the first conductor plane on the substrate, registration ink is deposited and allowed to dry thus forming temporary vias. A suitable dielectric paste is then deposited either on all the surface or except on viaslocations. The dielectric paste is then dried and fired. Firing however causes sublimation or evaporation of the temporary vias pattern leaving cavities in the dielectric layer. Slight buffing may be required to uncover the via holes. The vias and the second conductor plane are then deposited, dried and fired. The same steps are carried out for each subsequent conductor plane.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A process for constructing multilayer thick-film hybrid circuits on a surface of a substrate comprising in sequence the following steps: depositing, drying and then firing a first conductor plane by screen printing a thick-film conductor paste on the substrate, depositing registration ink by screen printing for making temporary vias, drying said registration ink, depositing by screen printing a thick-film dielectric paste over the surface of said substrate but not over said temporary vias, drying said dielectric paste, firing said temporary vias, drying said dielectric paste, firing said dielectric paste, said registration ink consisting of a substance whose point of sublimation or evaporation is slightly below the firing temperature of said dielectric paste, and, after sublimation or evaporation of said registration ink, depositing by screen printing additional conductor material, drying and firing said additional conductor material for forming a second conductor plane and filling the via holes and making connection with said first conductor plane. 
     
     
       2. A process as defined in claim 1 for constructing additional conductor planes interleaved with additional layers of dielectric material having vias therein filled with conductor material, comprising for each additional conductor plane, the said sequence of steps for applying the registration ink, the dielectric paste and the additional conductor material, and further including buffing the surface of each layer of dielectric paste once fired around any via holes therethrough. 
     
     
       3. A process as defined in claim 2, wherein the step of forming the conductor material in any additional layers of dielectric material and the additional conductor plane immediately above that said layer of dielectric material comprises first depositing a vias pattern of said conductor paste on said layer of dielectric material, drying and then firing said last mentioned conductor paste and then depositing additional conductor material thereover to form said additional conductor plane. 
     
     
       4. A process as defined in claim 1 wherein the step of depositing the additional conductor material comprises first depositing a vias pattern of said conductor paste, drying and then firing said last mentioned conductor paste and then depositing additional conductor material thereover to form said second conductor plane. 
     
     
       5. A process for constructing multilayer thick-film hybrid circuits on a surface of a substrate comprising in sequence the following steps: depositing, drying and then firing a first conductor plane by screen printing a thick-film conductor paste on said surface, depositing registration ink by screen printing for making temporary vias on said conductor plane, drying said registration ink, depositing by screen printing a thick-film dielectric paste over the whole of said surface, drying and then firing said dielectric paste, said registration ink consisting of a substance whose point of sublimation or evaporation is slightly below the firing temperature of said dielectric paste, said process also comprising the following sequential steps of buffing the surface of said fired dielectric paste just sufficiently to remove any extra fired dielectric paste around the via holes, depositing, drying and then firing a second conductor plane over the buffed surface of the dielectric layer for filling said via holes and making connection with said first conductor plane. 
     
     
       6. A process as defined in claim 5 including as a series of additional steps immediately preceeding the step of depositing said second conductor plane: depositing a vias pattern of said conductor paste, drying and then firing said last mentioned conductor paste.